2 Answers
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That is called 「ムードの『た』」 = the "modal 'ta'", not the past tense 'ta'. It is used when one's expectation has just matched or failed to match reality.

The female speaker of the sentence above knows that the male listener has expected her to be pretty, but he has just found out that she is not so. In this situation, the speaker will use 「悪かった」 = "Too bad!", not 「悪い」, even though it is happening at the present moment.

「あんまり[広]{ひろ}い[部屋]{へや}じゃなくて悪いな。」 = "Sorry this is not such a big room!"

In this case, 「悪い」 is in the plain present tense = "Sorry about that!". The speaker knows, as well as the listener, that the listener was in no position to expect a large room in the first place.

For comparison, here is an example of the past-tense 「悪かった」.

「あの[時]{とき}は、いい部屋が[空]{あ}いてなくて[本当]{ほんとう}に悪かった。」 = "At that time, I was really sorry that we didn't have a nice room available (for you)."

「あの時」 alone should tell us that this sentence is about a time in the past.

Without further context, it is impossible to tell whether this is the modal 'ta' or the past-tense 'ta'. It would, however, be safe to say that this phrase is more often used when one has just found out that something/someone is OK -- in other words, within the modal 'ta' territory = "I am relieved ~~".

Other examples of the modal 'ta':

When you have just found an item you have been looking for, you will say 「あった」, not 「ある」.